XE2 vs XE2S

I'll add me agreement to the excellent summation of the other posters.  I too was looking for a backup body for my X-E3.  Research led me to the same conclusion.  I was able to find X-E2 cameras for usually $100 less than X-E2s.  I paid $260 for my X-E2.

The X-E2 I bought had never had a firmware upgrade, it was on version 1.x.  As soon as it arrived, I did a quick function test.  Everything worked, but compared to my X-E3, it seemed "clunky".  I downloaded version 4.1.1 and followed the instructions, making sure I did a reset before doing the update.  The update finished successfully, but I thought I had bricked the camera.  The LCD would not display and when I turned the switch to off, the camera stayed on.  I had to remove the battery. I kept fiddling with it and finally got the menu in the EVF.  I navigated to reset, clicked "OK" and bam!  the camera came to life.  The camera after upgrade was a totally different camera, much more in line with my X-E3.

I find in casual use it is similar to my X-E3 in responsiveness, certainly fine for typical travel photography and portraits.  I was asked to photograph the back yard wedding of our close friends' son over the weekend (I was a full time pro in the film days). Between the two cameras, I shot ~1,100 frames. The fast pace of the wedding demonstrated the difference between the two and showed that the X-E3 upgrade was a lot bigger than casual shooting would indicate.  AF was noticeably faster on the X-E3, but the X-E2 was good enough in most instances. Saving images was noticeably slower with the X-E2.  This was really noticeable in burst mode.  I couldn't shoot more than 3 frames (Fine + RAW) before the camera stopped shooting and took a second to write to the card. The X-E3 would happily shoot 16 or more frames before stopping to write to the card, with a much shorter recovery time.

BTW, most of what I shot was with the 23mm f1.4 and the 56mm f1.2.  They make a great set.  I did take some images with the Rokinon 12mm, the 18-55 and the 55-200.

I have been very pleased with my X-E2 as a backup. Switching from one to the other in fast paced situations was no problem.  I'm hoping that in the future Fuji will release the X-H2 with all the goodies in the X-T3.